Times Square, the post-9/11 epicenter of worry in New York City, was packed with people and vehicles in the few hours after the Boston bombings, but there was little visible sign of a swelling police presence.

Tourists thronged the sidewalks and storefronts, joined by thousands leaving their offices at the end of the workday and sticking to their normal routes of subways, buses, trains, and parking garages. A headline on the Boston bombings took its turn among other stories crossing an overhead news ticker, but a lot of people still didn't know about the blasts or didn't seem very concerned.

Tom Robinson, visiting from of Brockton, Ma., was shocked when he was told about the bombings. His wife and four children stared at each other and looked around nervously as he expressed shock about what was happening back home. Ulrik Pedersen of Denmark, visiting with his father and mother, had heard about the bombing but was unconcerned. The UN worker said he had spent the last five years in Afghanistan and Somalia and had seen plenty of bombings.

Police officers in ones and twos were filtering into the area but there wasn't the big show of force you might see on a weekend before a public event. A police helicopter lulled in place far overhead to the north. Two officers stood by a cruiser parked next to the NYPD's retractable observation tower near 7th Avenue and 47th Street, but it was squatting down unmanned on its trailer. "We're just here until further notice," said one of the cops.

A Columbia Pictures crew was setting up along a parked convoy of trailers and trucks stretching along 47th all the way from 7th to 6th Avenue, getting ready to film "London Calling" from 6 p.m. to 8 a.m. A few said police had been by to talk about their logistics but didn't mention anything out of the ordinary. Last summer the same street had a near-continuous police checkpoint for searching all trucks headed into Times Square.

However, police had ramped up their anti-terror efforts at landmarks and other potential terrorist targets in the bombings' wake, according to a law-enforcement source.

The NYPD had deployed its Critical Response Vehicles until more was known about the Boston situation, said Deputy Commissioner Paul Browne, and officers were monitoring live feeds from surveillance videos throughout the city.

Browne said as many as 100 of the response vehicles were being put in motion for immediate deployment to landmarks, hotels, and other possible targets of terrorist attacks.

“As law enforcement authorities investigate today’s explosions in Boston, I ask all New Yorkers to keep the victims and their families in your thoughts and prayers," Mayor Michael Bloomberg said in a statement. "I have spoken with Police Commissioner Ray Kelly, and the NYPD has stepped up security at strategic locations and critical infrastructure, including our subways."

Bloomberg said 1,000 NYPD officers have been "assigned to counter-terrorism duties."

The Metropolitan Transportation Authority said police presence at subway stations, tunnels, and bridges was being upgraded.

The city's fire department also was on alert.

New York Gov. Andrew Cuomo said state agencies had been placed on a heightened state of alert.